For the removal of a concretion from the interior of the body of a living creature, it may often be necessary first to break up the concretion, in order then to be able to remove it simply, for example by means of a suction device. Devices and methods based on the use of ultrasonic energy are often used for such disintegration. In this case disintegration of the concretion can be effected by means of instruments and equipment which operate with, or, without, contact with the concretion.
Those instruments which operate with contact with the concretion are usually equipped with a sonotrode in the form of a rod or tube, which is brought up to the concretion to be destroyed and is set in oscillation by an ultrasonic transducer. Because of the rod-like or tubular structure of the sonotrode, breaking up of a concretion is effected substantially by mechanical longitudinal oscillations transmitted thereto so that the concretion is merely pierced and the sonotrode must therefore, be applied at various sites on the concretion in order to achieve its complete destruction. The disintegration of the concretion is therefore prolonged, thereby increasing the stress on the patient.
DE-A-2219790 discloses a tubular ultrasonic oscillator equipped at its distal end with a loosely coupled rebound body provided with teeth intended to cause a hard concretion to burst by fracture. The time needed to cause the concretion to burst is, however, still too long because substantially only longitudinal oscillations are employed for disintegrating the concretion.
A device for the breaking down concretions in the ureter, by the application of a complex action by ultrasonic vibration and electrohydraulic shocks to the concretion is described in the DE-A-2733019. The sonotrode consists of a wire, the distal end of which is provided with teeth. The wire can also be provided at its distal end with longitudinal projections and grooves. For the transmission of ultrasonic vibration to the concretion, the distal end of the sonotrode is set in longitudinal and transverse oscillation by means of an ultrasonic transducer. The concretion is thus broken down under a regular milling action. The sonotrode is then exchanged for a probe, with which the concretion is further broken down according to the principle of electrohydraulic lithotripsy. The application of this device is extremely complicated and, therefore, time-consuming. Also, the use of electrohydraulic lithotripsy involves the risk that when the concretion bursts, the surrounding tissue is injured by the resulting fragments; diseases may consequentially develop.
A further device for the disintegration of urinary calculi is described in U.S. Pat No. 3,830,240. In this case also, it is proposed to disintegrate the concretion by means of a wire sonotrode. The sonotrode may be of different shape both at its connection piece to the transducer and also at its distal end, so that longitudinal and transverse oscillations can be produced at said distal end. By reason of the shape of the wire sonotrode at both its distal and its proximal regions, the sonotrode is very easily broken when in operation, with consequent injury to the surrounding tissue.